Thermostatic mixer



FIG. 1 is a perspective front view of a thermostatic mixer, showing my new design from the top, right side and front;

FIG. 2 is a right side elevational view thereof, the left side view being a mirror image;

FIG. 3 is a top plan view thereof; and,

FIG. 4 front elevational view thereof. 

CLAIM The ornamental design for a thermostatic mixer, as shown and described. 